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Dc machine
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q81 ⇒ The direction of rotation of a dc shunt motor can be reversed by
interchanging either field or armature terminals. [other wrong options] [Discuss in forum] the supply terminals. the field terminals only. the armature terminals only. |
Q82 ⇒ The current drawn by a 220 V dc motor of armature resistance
0.5 ω and back emf 200 V is 40 A [other wrong options] [Discuss in forum] 44 A 400 A 440 A |
Q83 ⇒ A dc shunt motor runs at rated speed. If its field circuit gets opencircuited,
then soon after this the motor speed would tend to increase. [other wrong options] [Discuss in forum] decrease. remain unchanged. fluctuate around its previous speed. |
Q84 ⇒ In case of a conductively compensated dc series motor, the
compensating winding is provided in series with the armature winding. [other wrong options] [Discuss in forum] in parallel with the armature winding. in parallel with the field winding. as a separate unit. |
Q85 ⇒ A dc shunt motor is running at 1,200 rpm, when excited with
220 V dc. Neglecting the losses and saturation, the speed of the
motor when connected to a 175 V dc supply is 1,200 rpm. [other wrong options] [Discuss in forum] 750 rpm. 900 rpm. 1,050 rpm. |
Q86 ⇒ If the load current and flux of a dc motor are held constant and
voltage applied across it armature is increased by 5%, the speed of
the motor will increase by 5%. [other wrong options] [Discuss in forum] reduce by 5%. remain unalternated. depends on other factors. |
Q87 ⇒ A series motor drawing an armature current of la is operating
under saturated magnetic conditions. The torque developed in the
motor is proportional to la [other wrong options] [Discuss in forum] 1/la 1/Ia2 Ia2 |
Q88 ⇒ If the flux of a dc motor approaches zero, its speed will approach infinity. [other wrong options] [Discuss in forum] approach zero. remain unchanged. between 0 and infinity |
Q89 ⇒ The horse power obtained from the motor shaft is called the BHP. [other wrong options] [Discuss in forum] IHP. useful output. none of these. |
Q90 ⇒ If the applied voltage to a dc machine is 230V, then the back emf,
for maximum power developed is 115 V [other wrong options] [Discuss in forum] 200 V 230 V 460 V |
Q91 ⇒ T and P are the developed electromagnetic torque and the shaft
power of a dc series motor. If losses are neglected, then for constant
terminal voltage T ∝ P2. [other wrong options] [Discuss in forum] T ∝ P. T ∝ 1/P. T ∝ √P. |
Q92 ⇒ Consider the following statements: The armature torque in a dc motor is a function of 1. Field flux 2. Armature current 3. Speed 4. Damping Which of the above statements is/are correct? 1 and 2 only. [other wrong options] [Discuss in forum] 1,2,3 and 4. 3 and 4 only. 4 only. |
Q93 ⇒ In a dc series motor, if armature current is reduced to 70% of its
original value, the torque of the motor will be reduced by 0.51 [other wrong options] [Discuss in forum] 0.49 0.5 0.7 |
Q94 ⇒ A dc series motor develops a torque of 20 Nm at 3 A of load
current. If the current is increased to 6A, the torque developed will
be 80 Nm [other wrong options] [Discuss in forum] 10 Nm 20 Nm 40 Nm |
Q95 ⇒ A dc series motor is running at rated speed without any additional
resistance in series. If an additional resistance is placed in series,
the speed of motor decreases. [other wrong options] [Discuss in forum] increases. remains unchanged. oscillates around the rated speed. |
Q96 ⇒ For higher values of armature current la the torque developed by
a dc series motor is proportional to la [other wrong options] [Discuss in forum] Ia2 √la 1/Ia2 |
Q97 ⇒ A dc shunt motor is running on no load at 600 rpm. If the motor is
run, on no load, continuously for 12 hours, the speed of the motor
after 12 hour run will exceed 600 rpm. [other wrong options] [Discuss in forum] be 600 rpm. fall below 600 rpm. be 450 rpm. |
Q98 ⇒ An unsaturated dc shunt motor drives a constant torque load at a
speed at 1000 rpm taking an armature current of 20 A when 230 V
is applied to the motor. If the applied voltage is reduced to 115V.
the motor runs at. 1000 rpm taking an armature current of 40 A. [other wrong options] [Discuss in forum] 500 rpm taking an armature current of 20 A. 1000 rpm taking an armature current of 20 A. 500 rpm taking an armature current of 40 A. |
Q99 ⇒ In a differentially compounded dc motor, if the shunt field gets
suddenly opened, the motor will first stop and then run in opposite direction as a series motor. [other wrong options] [Discuss in forum] run as a series motor, but at slower speed in the same direction. run as a series motor in the same direction at high speed. not work and come to stand still. |
Q100 ⇒ It is advisable to start a dc series motor with some load to limit the speed. [other wrong options] [Discuss in forum] limit the flux. limit the current. avoid sparking. avoid demagnetization offield system. |
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